I'm not a programer nor an expert on this subject by all means, but there are already a number of developers taking advantage of the current AVX set of instructions on x86 to run their latest crops of VIs. For instance, IK Multimedia's Modo Drums won't even run of a full blown 2010 Mac Pro because its Xeons lack the ability to run AVX. By the way, these plugins can't be emulated via Rosetta at all. Porting to Apple Silicon is no easy task in this case.
I think that investing on a SoC using ARM v8 at this point makes little sense as it will become obsolete way sooner that it should, given that widespread adoption of SVE2 under v9 will become a reality in a few years time. Of course, for most people SVE2 probably won't matter, but for those who rely on emulation/simulation software like many audio plugins, it will. Imagine buying an M1X and three, four years ahead it loses the ability to run the latest and greatest VIs? I like to keep my computers for at least 6-7 years, but that's me...
Hope this helps. There's a very interesting discussion about this on Gearspace.com if you're interested, by the way. Cheers!